Apparatus and method for feature edge detection in semiconductor processing

ABSTRACT

A method and apparatus is provided to identify material boundaries and assist in the alignment of pattern masks in semiconductor fabrication. The invention probes a layer step or feature edge of an individual wafer using spectroscopic reflectance to detect a change in the reflectance spectral response. In integrated circuit fabrication, a wafer is subjected to wafer fabrication processes to produce a number of individual layers on a semiconductor substrate. During processing a reflectometer, a light emitting and collecting device, emits a specific range of electromagnetic wavelengths which are reflected from the wafer surface. The intensity of the reflected light is monitored for changes which signify the detection of a feature edge. The use of a specific range of electromagnetic wavelengths with the reflectometer allows the apparatus to detect feature edges covered by visibly-opaque material. After a feature edge has been detected, positional information associated with the detected feature edge may be used to accurately align a pattern mask.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to semiconductor processing and, in particular,to a method and apparatus for improving the alignment of pattern masksto semiconductor wafers.

2. Description of the Related Art

Trends toward smaller critical dimensions in semiconductor processinghave caused an exponential increase in the precision with whichfabrication processes must be performed by the semiconductor devicemanufacturer. Semiconductor based integrated circuits are typicallymanufactured through the formation of a set of layers on a wafercontaining many integrated circuit areas which will later be separatedinto individual dies. Very thin layers of material are deposited one ontop of the other in patterns to form integrated circuit components. Onetechnique of deposition and patterning is photolithography wherein amaterial layer is first coated with a light-sensitive photoresist. Thephotoresist is exposed through a pattern mask of a desired circuitpattern. The exposed photoresist is developed to remove, depending uponthe type of photoresist used, either the exposed or unexposed resist.Etching and/or deposition processes are then used to create the desiredcircuit within the pattern created.

It is imperative to the process of photolithography that the patternmask be precisely aligned on a wafer during processing. The overlay ofthe mask, the measure of how accurately the pattern mask was aligned,will often determine whether the wafer will be functional or must bediscarded. Because each wafer must undergo numerous photolithographyprocessing steps, the alignment of each pattern mask, especially thelast ones used, is dependant upon the correct alignment of earliermasks. Poor overlay destroys the intended electrical properties of acircuit device on a wafer.

Prior art alignment approaches have used numerous methods for aligning apattern mask to a wafer. One such method is the formation or use ofreflective targets within the material layers deposited on a wafer priorto the alignment of the pattern mask. The targets, such as verticalscores or pronounced feature edges between two material layers, areilluminated by a light source and the resulting contrast created by thetarget is used to visually align the pattern mask. However, in wafers inwhich, for example, an oxide layer has been deposited in a siliconsubstrate such that the surfaces of the oxide and the substrate areeven, the system fails because no physically distinct feature edgeexists. In addition, the detection of minute feature edges is furthercomplicated after numerous material layers have been deposited on top ofthe feature edge which must be detected. Visibly opaque materials andvariations in colors between material layers will also degrade theperformance of such a system.

U.S. Pat. No. 5,343,292 (Brueck, et al.), U.S. Pat. No. 4,991,962(Kantilal Jain), and U.S. Pat. No. 4,631,416 (William Trutna Jr.) useinterferometry to establish a phase shift within reflected light tocreate target patterns for alignment of a mask. The phase shift of awide light beam as it encounters a feature edge, the boundary between asubstrate and a material layer which has been deposited into asubstrate, can be detected if that light beam is only reflected by thesubstrate material. A diffraction grating pattern will emerge in thereflected light and this can be used to align pattern masks. However,the existence of material layers above the edge to be detected dilutesthe precision of this measurement technique by weakening theinterference pattern. In addition, interferometry systems which relyupon a physically distinct edge are imprecise when two materials haveequivalent heights at the material boundary edge.

None of the described methods allows for in-line identification offeature edges to allow accurate and repeatable registration of patternmasks within the increasingly reduced critical dimensions made possibleby recent advancements in wafer fabrication.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus that is able toovercome some of the problems attendant the alignment of pattern masksin semiconductor fabrication of small critical dimension devices.

The above and other features and advantages of the invention areachieved by providing an apparatus for the detection of a layer step orfeature edge of a die or wafer using spectroscopic reflectance to detecta change in the reflectance spectral response at the step or edge. Thedetection of a feature edge may be used, for example, to align a patternmask for photolithography processing of the wafer.

In integrated circuit fabrication, a wafer is subjected to waferfabrication processes to produce a number of individual layers on asemiconductor substrate. During processing, a reflectometer emitselectromagnetic radiation having a predetermined wavelength range. Theintensity or reflectivity of the radiation which is reflected from thewafer is monitored for changes which signal the detection of a featureedge within or on the wafer. The use of a specific range ofelectromagnetic wavelengths with the reflectometer allows the apparatusto detect feature edges covered by material which is visibly opaque,that is the material is opaque or semi-opaque in the visible wavelengthrange of 400 nm to 700 nm. After a feature edge has been detected, theapparatus may be used to accurately align a pattern mask according tothe data collected by the reflectometer.

The above and other advantages and features of the present inventionwill be better understood from the following detailed description of thepreferred embodiment which is provided in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a preferred embodiment of the presentinvention;

FIG. 2 is a perspective view of a wafer used to illustrate a preferredembodiment of the present invention;

FIG. 3 is another perspective view of a wafer used to illustrate apreferred embodiment of the present invention;

FIG. 4 is a flow chart outlining the steps of the present invention;

FIG. 5 is a perspective view of a wafer used to illustrate a preferredembodiment of the present invention;

FIG. 6 is a graphical representation of reflectivity versus wavelengthfor the wafer of FIG. 5 measured in accordance with a preferredembodiment of the present invention;

FIG. 7 is a graphical representation of reflectivity versus wavelengthfor the wafer of FIG. 5 measured in accordance with a preferredembodiment of the present invention;

FIG. 8 is a perspective view of a wafer used to illustrate a preferredembodiment of the present invention;

FIG. 9 is a graphical representation of reflectivity versus wavelengthfor the wafer of FIG. 8 measured in accordance with a preferredembodiment of the present invention;

FIG. 10 is a perspective view of a wafer used to illustrate a preferredembodiment of the present invention; and

FIG. 11 is a graphical representation of reflectivity versus wavelengthfor the wafer of FIG. 10 measured in accordance with a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized, and thatstructural, logical and electrical changes may be made without departingfrom the spirit and scope of the present invention. Wherever possible,like numerals are used to refer to like elements and functions in thevarious figures of the drawings and between the different embodiments ofthe present invention.

A feature edge detection system in accordance with the present inventionis illustrated generally in FIG. 1. The detection system is part of anautomated wafer fabrication system for processing a wafer 20. The wafer20 is mounted for processing on a coordinate table 36 attached to a base38 capable of three dimensional movement along the X, Y, and Z axis,preferably at least along the plane of the surface of the wafer 20 whichis to be processed. An element 52, preferably a robotically controlledelement, grips pattern mask 50, and is capable of moving pattern mask 50in response to control signals from the controller 42. Reflectometer 32produces a radiation incident beam 34 which intersects with a surface ofthe wafer, preferably at an angle approximately perpendicular to thatsurface. The incident beam 34 is comprised of electromagnetic radiationhaving a predetermined wavelength range and may have a variablecross-sectional area depending upon the critical dimensions of thefeature edge which must be detected on the wafer 20. The wavelengthrange of the incident beam 34 is preferably between about 100 nm toabout 1000 nm. The reflected beam 60 is the reflection of incident beam34 which is then collected in the reflectometer 32. The reflectometerexploits the material property of reflectivity to operate. Reflectivityis the property of illuminated objects, e.g. a wafer, to re-radiate orreflect a portion of the incident electromagnetic radiation energy. Thereflectometer 32 measures changes in intensity or reflectivity of thereflected beam 60 relative to the intensity of the incident beam 34. Asillustrated in greater detail in FIG. 2, the intensity of the reflectedbeam 60 will be different than the intensity of the incident beam 34depending upon the wavelength range of the beam, the absorptioncoefficient of the wafer 20 layers 24, 26, 28, 30 and the substrate 22,and the distance traveled by the incident beam 34 and reflected beam 60through the material layers 24, 26, 28, 30. The intensity of thereflected beam 60 may be measured in relative terms of intensity and/orreflectivity to a standard which may chosen by an operator.

The reflectometer 32 is attached to a mount 40 which is preferablycapable of movement at least along the plane of the wafer 20. Preferablythe reflectometer 32 or the coordinate table 36 is also capable ofvertical or Z axis movement to allow focusing of the incident beam 34 onthe surface of the wafer 20. The incident beam 34 is moved along thewafer 20 through relative movement between the coordinate table 36 andthe mount 40. One is generally stationary, while the other is moveable.The movement of the coordinate table 36 or mount 40 is directed by thecontroller 42 (FIG. 1) responsive to information received from controlinterface 46. The coordinate table 36 provides support for the wafer 20and monitors the position of the wafer 20 in relation to a fixed pointor to the reflectometer 32. Coordinate table 36 is preferably a platformcapable of movement along the plane of the wafer 20 and transmitting aposition signal to the controller 42. The position signal is at leastthe x and y coordinates of the current position of the coordinate table36 within the plane of the wafer 20 relative to a fixed point. Thecoordinate table 36 is comprised of motors such as, for example,DC-motors, stepping-motors, pulsed motors, or rotary hydraulic motorsand may have a dedicated microprocessor or a general purposemicroprocessor programmed with a mathematical coordinate table capableof monitoring the current position of the coordinate table with relationto a fixed point. Operation of the coordinate table 36 may beaccomplished, for example, by control signals from the controller 42.Controller 42 is further connected to a display 44 capable of visuallydisplaying the data from reflectometer 32 in graphical form and acontrol interface 46, for example a keypad, which allows an operator tocontrol the use of the FIG. 1 detection system.

FIG. 2 shows in an enlarged fashion a portion of the FIG. 1 detectionsystem when in use. The wafer 20 at the illustrated stage of processingincludes a plurality of material layers 22, 24, 26, 28, 30. For example,a semiconductor substrate 22 is processed such that an oxide layer 24 isformed therein and visibly-opaque material layers 26, 28, 30 are formedin series over the substrate 22 containing the oxide layer 24. Featureedges 62 are formed at the boundary between the substrate 22 and theoxide layer 24. The substrate 22 of the wafer 20 may be any materialsuitable for use as a substrate for integrated circuit devices which arereflective in the usable spectrum (150 nm to 1100 nm wavelengths),preferably silicon (Si) or gallium arsenide (GaAs). Visibly-opaquematerial layers 26, 28, 30 may be any visibly-opaque material used inthe processing of integrated circuits such as, for example, polyimide,polysilicon, Wsix, Nitride, oxide or other resist coatings. Thin layersof metallization, e.g. aluminum, may also be present on the wafer 20 solong as they remain penetrable by the chosen wavelength range ofelectromagnetic radiation incident beam 34 being used. For example, oneor more metallization layers comprised of one or more of a group ofmetals including titanium, copper, aluminum, platinum, and tungstenhaving a thickness of less than approximately 500 Angstroms would notsignificantly degrade the radiation incident/reflected beams 34, 60 usedin the present invention.

Preferably the beam intersects the wafer 20 perpendicular to the planeof the wafer 20. The incident beam 34, depending upon the predeterminedwavelength range, will pass through visibly-opaque material layers 26,28, 30 and oxide layer 24 to the substrate 22. The beam is reflected bythe substrate 22 and reflected beam 60 and is collected in thereflectometer 32. As shown in FIG. 2, the reflectance path of reflectedbeam 60 is different on the left and right sides of a feature edge 62.

FIG. 3 shows a pattern mask 50 such as is commonly used in integratedcircuit manufacture which is aligned on the wafer 20 such that a featureedge 62 of the mask 50 is parallel to the feature edge 62 separating twolayers of wafer 20, for example the substrate 22 and the material layer24. An element 52 moveable in two or, preferably, three dimensionspositions the mask 50 responsive to control signals from the controller42.

The reflectometer 32 may be any device capable of producing anelectromagnetic incident beam 34 of a predetermined wavelength rangedirected at the wafer 20 and collecting reflected beam 60 to measure theintensity or reflectivity of the reflected beam 60 over thepredetermined wavelength range. The controller 42 is preferably ageneral use microprocessor capable of receiving input from thereflectometer 32, the control table 36, and the input interface 46. Thecontroller 42 may be dedicated to the system 5 or may be used to controlother wafer fabrication processes as well.

The process for implementing the FIG. 1 detection system to align apattern mask 50 onto the wafer 20 will next be described with referenceto FIG. 4. The wafer 20, which may ultimately be diced and yield manydies, is subjected to integrated circuit processing such that at leastmaterial layer(s) 24 are formed on and/or within the substrate 22 instep S200. This may occur through etching, deposition, priorphotolithography processing, and other methods known in the art. Often,portions of the substrate 22 are removed and filled with an oxide toform material layers 24 which are substantially flush with the surfaceof the substrate 22. For example, a silicon substrate 22 may havesilicon oxide (SiO₂) layers 24 which are deposited in etched portions ofthe substrate 22, as shown in FIGS. 2, 3. Due to the small size of theoxide layers 24 and the similarity in color between a substratesemiconductor and an oxide of that semiconductor, e.g. Si and SiO₂,visual or interferometric inspection of the surface of the wafer 20 canbe insufficient to detect the feature edge 62 between the substrate 22and oxide layers 24. This is especially true in the case in whichseveral visibly-opaque material layers 26, 28, 30 have been depositedonto the wafer 20 in prior processing. Deposition of the visibly-opaquematerial layers 26, 28, 30 may be necessary to the processing of thewafer 20 prior to use of the mask 50.

Returning to FIG. 4, once the wafer 20 has been secured, the mask 50must be aligned to continue processing, e.g. to completephotolithography processing, of the wafer 20. The wafer 20 is placedonto and/or secured to the coordinate table 36 in step S202. The wafer20 may already be on the coordinate table 36 if the coordinate table 36has been used in prior processing steps. In step S204, the controller 42transmits control signals to the reflectometer 32 to begin emission ofthe incident beam 34. This step may be part of an automated process ormay be initiated by an operator using control interface 46. Thereflectometer 32 emits electromagnetic radiation in the form of anincident beam 34 directed towards at least one surface of the wafer 20in step S206. The incident beam 34 preferably has a minimum spot size,e.g. less than 10 microns in area, preferably less than about 1 micronin area in the form of a rectangle or other right angled shape. Thewavelength range of the incident beam 34 is chosen such that it passesthrough the material layers above the substrate 22 (e.g. material layers24, 26, 28 30) and is reflected from the surface of the substrate 22 asthe reflected beam 60 which is collected by the reflectometer 32 in stepS208. The reflectometer 32 measures the intensity of the reflected beam60 over the predetermined wavelength range and outputs the intensityreading to the controller 42 in step S210. The controller 42 displaysthe data from reflectometer 40 onto a display 44 in a form readable byan operator in step S212. One such display may be a graph of intensityversus wavelength or, alternatively, a graphical representation of thewafer 20 as reflected by the reflected beam 60. In step S214, thecoordinate table 36 and, therefore, the wafer 20 are moved along theplane of the wafer 20 or, alternatively, the reflectometer 32 is movedalong the plane of the wafer 20 such that the entire surface or aselected portion of the surface of the wafer 20 may be scanned.

A feature edge 62 is detected in step S216 by monitoring the signal fromthe reflectometer 32 for a sudden change in the intensity versuswavelength data output from reflectometer 32. If a sudden change orsharp derivation in intensity is detected, the operator or controller 42compares the change to known data for the specific chemical compositionof the substrate 22 and material layers 24, 26, 28, and 30 in step S218.If no feature edge 62 is detected of step S216, the signal from thereflectometer 32 continues to be monitored in step S214.

If the change corresponds to known data for a feature edge 62, thepositional data of the feature edge 62 in relation to the wafer 20 iscalculated and stored in controller 42 through the use of the coordinatetable 36 in step S218. In step S220 the operator or controller 42determines whether a sufficient number of feature edges 62, preferably aminimum of two, have been detected to allow for proper alignment of themask 50. The feature edge detection process may be repeated in step S206if additional feature edges 62 must be detected.

To further illustrate detection of a feature edge 62 through analysis ofthe derivation of intensity patterns, FIG. 5 shows a wafer 20 comprisedof a silicon substrate 22 and a variety of material layers including asilicon oxide layer 24 having a thickness of approximately 1000Angstroms and a Wsix layer 26 having a thickness of approximately 1250Angstroms. FIGS. 6-7 display graphical representations of reflectivityversus wavelength of the beams 34, 60 directed at and reflected fromsections 70 and 72 of the wafer 20, respectively. FIG. 6 corresponds tothe reflectivity pattern seen over a wavelength range of about 250 nm toabout 750 nm for the sections 70 of the wafer 20 which are comprised ofthe silicon substrate 22 and the Wsix layer 26. As the reflectometer 32,or alternatively, the wafer 20 itself, moves in a direction parallel tothe surface of the wafer 20, the graphical representation of theintensity versus the wavelength of the reflected beam 60 will change tothe intensity pattern as shown in FIG. 7, as the beam moves from section70 to section 72, the latter of which is comprised of the siliconsubstrate 22, silicon oxide layer 24, and Wsix layer 26. The obvioussignificant and sudden change in the graphical display signals thedetection of a feature edge 62. In this example the feature edgecorresponds to the boundary between the silicon substrate 22 and thesilicon oxide layer 24.

By way of further example, FIG. 8 shows a wafer 20 comprised of asilicon substrate 22 and a variety of material layers including asilicon oxide layer 24 having a thickness of approximately 90 Angstroms,a polysilicon layer 28 having a thickness of approximately 850Angstroms, and a Wsix layer 26 having a thickness of approximately 1250Angstroms. FIG. 9 is a graphical display representing reflectivityversus wavelength of the incident beam 34 and 60 directed at andreflected from section 76 of the wafer 20 of FIG. 8. FIG. 10 shows awafer 20 comprised of a silicon substrate 22 and a variety of materiallayers including a silicon oxide layer 24 having a thickness ofapproximately 1000 Angstroms, a polysilicon layer 28 having a thicknessof approximately 4000 Angstroms, and a Wsix layer 26 having a thicknessof approximately 1250 Angstroms. FIG. 11 is a graphical displayrepresenting reflectivity versus wavelength of the incident beam 34 and60 directed at and reflected from section 80 of the wafer 20 of FIG. 10.Known data such as that displayed in FIGS. 6, 7, 9, and 11 may be usedto compare reflectivity readings from a wafer 20 being measured usingthe apparatus and methods of the present invention to determine theexact material boundaries or feature edges of regions 76 (FIG. 8) and 80(FIG. 10).

Returning to FIG. 4, once one or more feature edge 62 have beendetected, the controller 42 determines the position of the incident beam34 relative to the wafer 20 using the coordinate table 36 which monitorsthe position of the wafer 20 on two or three dimensions. Next, a controlelement 52 positions the mask 50 over the wafer 20 responsive topositional data from controller 42 in step S222. The positioning of themask 50 may be accomplished by a human operator through controlinterface 46 or by the controller 42 in an automated fabricationproduction line. The wafer 20 may then be subjected to photolithographyor other processing techniques requiring correct alignment of a patternmask in step S224.

The feature edge detection system of the present invention may beimplemented at various stages within a semiconductor wafer fabricationproduction line. The detection system may be used prior to deposition ofone or more of the material layers 26, 28, 30 and a plurality ofdetection systems may be implemented within the same wafer fabricationproduction line to assist in the identification of feature edges 62 onwafers 20 whenever such identification is requited or desired.

With the present invention, the identification of material layer featureedges 62 in a wafer 20 by a human or machine at any stage of a waferfabrication process is simplified and does not suffer from theobfuscation which occurs in current optical systems and, therefore,allows for precise and repeatable registration of masks onto wafers 20.

It should be readily understood that the invention is not limited to thespecific embodiments described and illustrated above. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, which are commensurate with the spirit and scope of theinvention. Accordingly, the invention is not limited by the foregoingdescription, but is only limited by the scope of the appended claims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. An apparatus for the detection of materiallayer boundaries in a semiconductor wafer, said apparatus comprising: anelectromagnetic radiation source for emitting an electromagneticradiation beam directed at a mounting surface for a wafer, saidelectromagnetic radiation beam having a property that it will bereflected by a material layer of a wafer when the wafer is mounted onsaid mounting surface; an electromagnetic radiation detector positionedto receive a reflected electromagnetic radiation beam and for measuringthe intensity of the electromagnetic radiation beam after theelectromagnetic radiation beam has been reflected from a material layerof a wafer; a system for moving said radiation source and detectorrelative to said wafer mounting surface such that said electromagneticradiation beam and associated reflected beam scan an area of a wafermounted on said mounting surface; and a device coupled to said detectorfor determining a change in intensity of said reflected beam when saidradiation beam scans over a boundary region of a material layer of awafer mounted on said mounting surface.
 2. The apparatus of claim 1,wherein said source is part of a reflectometer.
 3. The apparatus ofclaim 1, wherein said detector is part of a reflectometer.
 4. Theapparatus of claim 1, wherein said source and said detector arecontained within a single reflectometer.
 5. The apparatus of claim 1,wherein said electromagnetic radiation beam has a range of wavelengthsbetween about 100 nm to about 1000 nm.
 6. The apparatus of claim 1,wherein said electromagnetic radiation beam has a spot size has an areaof less than about 10 microns in the form of a rectangle.
 7. Theapparatus of claim 1, wherein said electromagnetic radiation beam has aspot size has an area of less than about 1 micron in the form of arectangle.
 8. The apparatus of claim 4, wherein said reflectometer ispositioned relative to said mounting surface such that theelectromagnetic radiation is incident said mounting surface atapproximately a right angle.
 9. The apparatus of claim 4, wherein saidsystem moves said reflectometer along at least a plane of said mountingsurface.
 10. The apparatus of claim 9, wherein said system also movessaid reflectometer in a direction perpendicular to the plane of saidmounting surface such that the emitted electromagnetic beam from saidreflectometer may be focused on a wafer when mounted on said mountingsurface.
 11. The apparatus of claim 4, wherein said mounting surface isa platform for holding said wafer.
 12. The apparatus of claim 11,wherein said system moves said platform along at least a plane of saidmounting surface.
 13. The apparatus of claim 11, wherein said systemmoves said platform in a direction perpendicular to the plane of saidmounting surface such that the emitted electromagnetic beam from saidreflectometer may be focused on a wafer when mounted on said mountingsurface.
 14. The apparatus of claim 4, wherein said device includes adisplay device which displays the intensity of said reflected beam as itmoves relative to said mounting surface.
 15. The apparatus of claim 4,wherein said device includes a controller which associates a location ofsaid mounting surface relative to said emitting radiation beam when saidchange in intensity is determined.
 16. The apparatus of claim 15,wherein said controller controls the positioning of a processing maskrelative to a wafer when mounted on said mounting surface usingpositional information associated with said change in intensity.
 17. Theapparatus of claim 15, wherein said controller further comprises acoordinate table connected to said controller and at least one of saidmounting surface and said reflectometer for determining the relativepositions of at least one of said reflectometer and said mountingsurface.
 18. The apparatus of claim 15, further comprising an inputdevice coupled to said controller for receiving input from an operator.19. The apparatus of claim 1, further comprising a wafer mounted on saidmounting surface for scanning by said electromagnetic radiation source.20. A method of identifying a material layer boundary in a semiconductorwafer comprising the steps of: emitting an electromagnetic radiationbeam directed at a surface of the wafer, said electromagnetic radiationbeam being emitted from a reflectometer and having a property that itwill be reflected by a material layer of said wafer; measuring theintensity of the electromagnetic radiation beam with said reflectometerafter the electromagnetic radiation beam has been reflected from saidlayer; and monitoring the measured intensity of the reflectedelectromagnetic radiation beam for a change in intensity.
 21. The methodof claim 20, wherein said property of said electromagnetic radiationbeam is said electromagnetic radiation beam having wavelengths in therange between about 100 nm to about 1000 nm.
 22. The method of claim 20,further comprising the step of positioning said reflectometer relativeto said wafer such that the electromagnetic radiation beam is incidentsaid wafer at approximately a right angle.
 23. The method of claim 20,further comprising the step of moving at least one of said wafer or saidreflectometer such that said step of measuring may be accomplished fordifferent sections of said wafer.
 24. The method of claim 23, whereinsaid step of moving further comprises monitoring the relative positionsof said wafer and said reflectometer to a fixed point or each other. 25.The method of claim 20, wherein said step of monitoring furthercomprises moving said reflectometer along a plane parallel to saidsurface of said wafer.
 26. The method of claim 20, wherein said step ofmonitoring further comprises focusing said electromagnetic radiationthrough movement of said reflectometer along a plane perpendicular tosaid surface of said wafer.
 27. The method of claim 26, wherein saidelectromagnetic radiation beam has a spot size area of less thanapproximately 10 microns in the form of a rectangle.
 28. The method ofclaim 26, wherein said electromagnetic radiation beam has a spot sizearea of less than approximately 1 micron in the form of a rectangle. 29.The method of claim 20, further comprising the step of displaying atleast one of the results of said step of measuring and said step ofmonitoring using a graphical representation.
 30. The method of claim 20,further comprising the step of incorporating said reflectometer into aproduction line of said wafer.
 31. The method of claim 30, wherein saidstep of incorporating is accomplished by locating said reflectometerwithin said production line before an area where said wafer is subjectedto photolithography.